Re: IPv4 specific issue with USB tethering between my Debian laptop and my phone

[Dan Ritter <dsr@randomstring.org>]

Vincent Lefevre wrote: 
> Hi,
> 
> When I use USB tethering between my Debian/unstable laptop and my
> Samsung Galaxy Note10+ phone (Android 11), everything is OK with
> IPv6 connections (e.g. "wget -6"), but IPv4 connections freeze
> (e.g. "wget -4" or "ssh -4"). I can notice this in particular when
> testing with the same remote server. For instance, with "wget -4",
> a few dozens of KB are downloaded, then the connection is completely
> frozen.
> 
> I don't have any issue with the mobile hotspot (thus wifi between the
> laptop and the phone) or with a Cosmo under Android 9 (instead of the
> Samsung Galaxy Note10+), but in both cases, this is much slower, and
> I sometimes get wifi disconnections.
> 
> On my Debian laptop, I'm using NetworkManager (nmcli).

Have you investigated the MTU? This sounds like a mismatch
between what your laptop and phone are using.

Diagnosis (besides looking at connection details on both sides):
ping with increasingly large packet sizes. If it works at small
IPv4 packet sizes and then stops, that's the problem.

-dsr-